2.5.4

Duplicate registrations now produce explicit startup errors before the SDK contacts Server or polls work.

• DuplicateRegistrationError identifies the registration kind, wire name and both definitions. It is both an SDK error and a ValueError.
• Workers reject duplicate workflow and activity names. Workflow definitions reject conflicting signal, query, update and validator names within each handler kind.
• Worker, Replayer and test-environment admission check programmatically defined classes too.
• Normal Python method overrides remain supported. Names stay scoped by worker and handler kind. Same-class test environment registration is idempotent, and explicit activity mock setters allow replacement.

Resolve a conflict by removing the duplicate registration, choosing one implementation for that Worker, or overriding the same Python method attribute deliberately. Existing durable history and public wire formats are unchanged.

Qualification covers the full Python3.10–3.12 suites, official replay admission fixtures and connected Server integration. A fresh PyPI installation verifies the public error and all36 registration controls before the ordinary website and sample pointers advance.